Carpet backed with thixotropic polyurethane adhesive

ABSTRACT

A carpet backing is formed by applying a thixotropic polyurethane adhesive composition as either a laminating adhesive, a precoat adhesive or a unitary backing to the underside of the primary fabric of tufted carpet. The thixotropic adhesive composition, comprising a liquid, hydroxyl-terminated diene polymer, a low molecular weight reinforcing polyol, an isocyanate, a filler, and a catalyst, provides substantially complete bundle wrap of each fiber tuft without penetration through the primary fabric backing material to the top side or face of the carpet. The thixotropic polyurethane adhesive composition is applied to the underside of the primary fabric backing material in measured quantity and cured by the application of heat with or without a secondary fabric being applied prior to curing.

United States Patent [1 1 Sheffler et al.

[ CARPET BACKED WITH THIXOTROPIC POLYURETHANE ADHESIVE [75] Inventors: Robert H. Sheffler, Harleysville, Pa.;

Robert Koncos, Moorestown; Kenyon A. Riches, Cherry Hill, both of NJ.

[73] Assignee: Atlantic Richfield Company,

Philadelphia, Pa.

[22] Filed: July 5, 1973 [21] Appl. No.: 376,496

[52] US. Cl 428/94; 428/97 [51] Int. Cl. D03d 27/00; D04h 11/00 [58] Field of Search 161/62-67, 161/190; 260/37 N, 40 TN; 156/72, 435;

[56] References Cited UNITED STATES PATENTS 3,664,863 5/1972 Dijkhuizen 161/66 3,705,834 12/1972 Terry ..l6l/19O [451 July 15,1975

5/1973 Lovell 161/66 [57] ABSTRACT A carpet backing is formed by applying a thixotropic polyurethane adhesive composition as either a laminating adhesive, a precoat adhesive or a unitary backing to the underside of the primary fabric of tufted carpet. The thixotropic adhesive composition, comprising a liquid, hydroxyl-terminated diene polymer, a low molecular weight reinforcing polyol, an isocyanate, a filler, and a catalyst, provides substantially complete bundle'wrap of each fiber tuft without penetration through the primary fabric backing material to the top side or face of the carpet. The thixotropic polyurethane adhesive composition is applied to the underside of the primary fabric backing material in measured quantity and cured by the application of heat with or without a secondary fabric being applied prior to curing.

1 Claim, No Drawings CARPET BACKED wrrn THIXOTROPIC POLYURETHANE ADHESIVE FIELD OF THE INVENTION The present invention relates to thixotropic adhesive compositions, their application to carpets, and to the resulting carpet material. More particularly, the present invention is directed to thixotropic polyurethane adhesive compositions which can be advantageously applied to carpets as a unitary backing, a precoat adhesive, or a laminating adhesive, the application of such compositions and the resulting carpet material.

BACKGROUND OF THE INVENTION The tufting method which is now generally employed for the manufacture of carpets comprises looping pile fibers of natural or synthetic material through a relatively inexpensive woven or non-woven textile base, known as the primary fabric backing material. Short loops of the long pile fibers are pushed through the primary fabric backing material such that one single continuous length of fiber constituting a complete row of pile in the carpet is formed. The elongated loops extending from the base (the top side) of the primary fabric backing material can remain connected or severed, depending on whether a loop pile or a cut pile carpet is desired. The loops on the bottom side of the carpet are not cut. These pile loops or tufts are not securely fastened in the tufting process. Without additional anchorage these fibers or the tufts can be pulled from the primary fabric or otherwise disarrayed. Necessary anchorage is provided by applying an adhesive material in liquid form to the underside of the carpet. The adhesive applied to the underside of the carpet is accordingly of major importance to the quality and performance of the carpet. It retains the pile fibers or tufts in place, secures the individual fibers of the yarn, prevents pilling of the yarn and controls dimensional stability.

Without additional backing material applied to the adhesive material on the undeside of the carpet, the carpet is said to have a unitary backing. Carpets having a unitary backing are used principally as commercial carpeting. If a sponge like material (or foam) is applied after the adhesive material is applied, the adhesive coating is referred to as a precoat composition. Uncured foam material can be applied directly to the precoated carpet back and cured in place, or it can be cured as a separate sheet and then laminated to the back of the carpet by means of the precoat or use of another adhesive. The precoat provides good tuft lock, while the foam material, such as polyvinyl chloride or styrene butadiene copolymer, serves as a cushion back for the carpet.

For the standard double back carpet, the adhesive layer is referred to as a laminating adhesive. After the laminating adhesive is applied to the underside of the primary fabric backing material of a double back car pet, a further backing layer of secondary fabric material, known as the scrim, is applied to the coated underside of the carpet. The scrim serves to improve dimensional stability, appearance of the carpet and also the enhance tuft lock, i.e., the strength with which the fibers are retained in the primary fabric backing. The laminating adhesive for double back carpets serves not only to anchor the pile fabers or tufts, but also to adhere the scrim to the carpet. Conventionally, in the process of making double back tufted carpets the laminating adhesive is applied in liquid form to the underside of the carpet and the scrim is applied to the same side while the laminating adhesive is still wet and uncured. The carpet is then passed through an oven to dry and cure the laminating adhesive.

When reference is made herein to carpets, it will be understood that any fabric like sheet material is contemplated, whether tufted, woven, knitted, felted, cemented or otherwise, and that the fabric can be a carpet, rug, mat, floor covering, floor tile, wall covering or the like. The primary fabric is normally a material such as jute, burlap or polypropylene. The scrim or secondary fabric can consist of natural and/0r synthetic materials, such as jute, hessian, burlap, nylon, polypropylene and the like. The pile fibers can also be natural or synthetic materials, such as wool, polyacrylate, cellulose acetate, polyester, nylon, polyacrylonitrile, polypropylene and the like, as well as mixtures of such materials.

Styrene butadiene rubber latex or carboxylated styrene butadiene rubber latex of the type commonly employed as a laminating adhesive has several known disadvantages. Such adhesive requires a long cure time at relatively high temperatures (e.g., 300F. for 8 to 10 minutes) and this means that large expensive curing ovens must be employed. With certain heat sensitive fibers that require lower curing temperatures, even longer curing times are necessary. Carboxylated styrene-butadiene latex adhesive may have a strong odor of ammonia associated with it and sometimes finished carpets have a heavy and unpleasant odor of styrene. In addition, carboxylated butadiene-styrene polymer adhesives can contain some residual unsaturation which tends to cause unsatisfactory aging characteristics, resulting in a loss of flexibility. In fact, polymerization which occurs as a result of such residual unsaturation has caused the backing of carpets and rugs to become stiff after only a few years. Another disadvantage of carboxylated styrene butadiene rubber latex adhesive is the required method of application. In general a pan coater consisting of a latex pan, one or two adjustable doctor or striker bars, one or two variable speed coater rolls and one or two adjustable tension rolls are required for the application of such adhesive. These require a fairly high degree of operator skill and attention to achieve a proper degree of penetration of adhesive into tufts. It is important that the adhesive employed for carpets not migrate past the primary backing fabric to the face or top side of the carpet since this migration can cause the yarn to become stiff and render the final carpet unacceptable. If the settings are not correct for the particular type of yarn used rejects become quite high. Quality of the finished carpet thus becomes highly dependent on operator skill and conscientiousness and increased expenses are incurred from the fact that several employees are required to operate the equipment. Another disadvantage is the poor green strength of carboxylated styrene butadiene rubber latex adhesive. If effective adhesion does not occur until near the end of a curing cycle the chances of delamination and product waste increase greatly. The advent of certain synthetic materials in the carpet industry which permit a carpet to be used both indoors and outdoors has given rise to further problems in connection with the preparation or the manufacture of carpeting. Polypropylene is a relatively cheap material which in most respects is quite satisfactory for use as the pile fiber, the primary fabric backing material, and the scrim, or the secondary fabric substrate, or a carpet. However, polypropylene presents an adhesion problem since latex compositions normally employed in carpet manufacture do not adhere well to the surface of polypropylene. Carpets prepared from polypropylene have been subject to delamination of the scrim or secondary fabric substrate. In order to overcome this problem attempts have been made to employ multiple intervening adhesive layers, resulting in increased production costs.

SUMMARY OF THE INVENTION An object of the present invention is to provide improved adhesive compositions which find particular application for rug and carpet backing applications.

Another object of the present invention is to provide a solvent-free polymer composition to avoid evaporation of water and/or organic volatile materials into the atmmosphere while curing.

A further object of the present invention is to provide improved thixotropic polyurethane adhesive compositions which can be used as carpet backing adhesive.

Still a further object of the present invention is to provide low cost adhesive compositions which have excellent adhesion with respect to natural and synthetic materials and good resistance to aging.

Yet another object of the present invention is to provide thixotropic polyurethane compositions which can be used as unitary backing, precoat adhesive or laminating adhesive for carpets.

Another object of the present invention is to provide improved procedures for applying carpet backing adhesive compositions.

A still further object of the present invention is to provide carpet material having good tuft lock and bundle wrap.

The thixotropic adhesive compositions provided in accordance with the present invention comprise a mixture of a liquid hydroxyl-terminated diene homopolymer or copolymer, a low molecular weight polyol, an isocyanate, a filler, and catalyst. These compositions have an initial Brookfield viscosity of between about 3,000 and about 100,000 centipoises at 5 rpm using a number 5 spindle. More especially, the adhesive compositions of the invention comprise a mixture of a liquid hydroxyl-terminated diene homopolymer or copolymer, a polyol having an equivalent weight of between about 50 and about 300 present in an amount up to 5 times the equivalents of diene polymer; a polyol having an equivalent weight of between about 50 and about 300 present in an amount between about 1.5 and about 8 times the equivalents of diene polymer; an isocyanate material having a functionality of between 2 and 3 present in an amount to provide a NCO/OH equivalents ratio of between 0.95:1 and 1.5:1; at least one filler present in an amount of between about 40 and about 800 parts per 100 parts by weight of diene polymer; an oil extending hydrocarbon liquid present in an amount up to 200 parts per 100 parts by weight of the diene polymer; water present in an amount up to 10 parts per 100 parts by weight of the diene polymer; and at least one catalyst capable of accelerating the cure time of the composition, present in an amount between about 0.02 and about 4 parts per hundred parts by weight of the diene polymer. The resulting composition has an initial Brookfield viscosity at 5 rpm using a number 5 spindle of between about 3,000 and about 100,000 and the ratio of the viscosity at .1 rpm and 20 rpm for the thixotropic composition is between about 1.3: and 10:1. Conventional additives such as oxidation inhibitors, pot life inhibitors, stabilizers, pigments and the like can be incorporated in the adhesive compositions for improved characteristics.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The polymeric materials combined with isocyanate to produce the urethane adhesive compositions of the present invention are liquid, hydroxyl-terminated diene homopolymers and copolymers. The polymers possess predominantly primary, terminal hydroxyl groups of the allylic type and have a hydroxyl content of between about 0.6 and about 0.9 milliequivalents per gram and a viscosity at 30C. of between about 30 and about 300 poises. The structure of the polymers accounts for their high reactivity, especially with aromatic diisocyanates. Oil extension, using low cost process oils, provides formulation flexibility in controlling properties while the liquid systems are uncured, such as viscosity pot life, gel time and the like, as well as properties of the cured product, including flexibility, out growth, elongation and the like. I

Hydroxyl terminated homopolymers and copolymers contemplated for the present invention are disclosed in more" detail in US. letters Pat. Nos. 3,637,558, 3,674,743 and 3,714,1 10, which patent disclosures are specifically incorporated by reference herein. These patents disclose polymers which have an average of at least 2.1 and preferably between about 2.1 and about 2.5 predominantlyprimary, terminal allylic hydroxyls per molecule and being an addition polymer of 0 to percent by weight of an alpha-monoolefinically unsaturated monomer of 2 to 12 carbon atoms, the balance consisting essentially of a 1,3-diene hydrocarbon of about 4 to about 12 carbon atoms, said polymer having the majority of its unsaturation in the main hydrocarbon chain and a number average molecular weight of about .400 to about 25,000 as determined by cryoscopic, ebullioscopic and osmometric methods.

As disclosed in the aforementioned patents, the dienes which can be employed are unsubstituted, 2- substituted or 3,3-disubstituted 1,3-dienes of up to about 12 carbon atoms. The diene preferably has up to six carbon atoms and the substituents in the 2- and/or 3-position can be hydrogen, alkyl, generally lower alkyl, e.g., of one to four carbon atoms, aryl (substituted or unsubstituted), halogen, nitro, nitrile, etc. Typical dienes which can be employed are 1,3-butadiene, isoprene, chloroprene, 2-cyano-l,3-butadiene, isoprene, chloroprene, 2-cyano-l,3-butadiene, 2,3-dimethyl-1,3- butadiene, etc.

Olefinically unsaturated monomers which can be incorporated into the diene polymer products used in this invention include alpha-mono olefinic materials of about two or three to 10 or 12 carbon atoms such as styrene, vinyl toluene, methyl methacrylate, methylacrylate, acrylic esters, vinyl chloride, vinylidene chloride, etc. Acrylonitrile, acrylic acid, vinylidene cyanide, acrylamide,.etc., provide lowmolecular weight hydroxy-terminated diene intermediate copolymers which have sites suitable for cross-linking. As can be seen, the usable olefinic monomers can be ethylenes, substituted with halogen, aromatic hydrocarbon, or even cyano or carboxylcontaining radicals in some instances. The choice and amount of mono olefinic monomer employed will often be determined on the basis of properties desired. Generally the amount of monoolefinic monomer in the polymer will be about 0-75 percent by weight of the total addition polymer, preferably about 1 to 40 percent, or even about 40 percent.

Specific hydroxyl-terminated homopolymers contemplated for the present invention are those having the general formula:

where n 44 to 65. Specific examples include resin R-45M having an equivalent weight of 1330 and a hydroxyl content of 0.75 milliequivalents per gram; where n equals 44 to 60. Another example is resin R-45l-IT having an equivalent weight of 1,180 and a hydroxyl content of 0.85 milliequivalents per gram where n equals 57 to 65.

Specific hydroxyl-terminated copolymers contemplated for the present invention are those having the general formula: I

where a 0.75, b =0.25, n 57 to 65, and X is the styrene moiety. An example of such a styrene-butadiene copolymer is resin CS- which has an equivalent weight of 1530, an iodine number of 335, and a hydroxyl content of 0.65 milliequivalents per gram.

The low molecular weight reinforcing polyols which can be employed in the present invention in order to obtain improved tensile strength, tear strength and adhesion are those polyols having an equivalent weight of between about 50 and about 300 and preferably those which have an average equivalent weight of between about 90 and about 250. The contemplated polyols, which can be di, tri or tetra functional, should have an average functionality of between 2.0 and 2.5. In general, these polyols are employed in an amount between about 1.5 and about 8 times the equivalents of liquid, hydroxyl-terminated diene polymer utilized in connection with the invention. Although bisisopropanol aniline is a preferred polyol for the invention, other polyols which can be used include bisisopropanol bisphenol A, 2-ethyl-l, 3-hexanediol, dipropylene glycol, diethylencglycol and bisisopropanol isophthalate.

Higher equivalent weight polyols, having an equivalent weight of between about 500 and about 2200, can also be included in an amount up to about 5 times the equivalents of diene polymer, preferably between about 0.1 and about 5.0 times the equivalents of liquid, hydroxyl-terminated diene polymer. For example, polypropylene glycol can, if desired, be included in the fire retardant polyurethane compositions.

Isocyanates which can be employed to form the polyurethane upon reaction with the liquid, hydroxylterminated diene polymers include tolyene diisocyanate (TDI), diphenyl methane 4, 4diisocyanate (MD!) and polymeric diisocyanates such as polyphenylmethane polyisocyanate (PAPI). Other isocyanate materials which can be used to produce urethane resin compositions of this invention include any one of a number of materials containing two or more isocyanate radicals, such as 1,5-naphthalene diisocyanate, phenylene diisocyanates, trans-vinylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, 3,3'-dimethoxy-4,4-biphenyl diisocyanate, as well as related aromatic and aliphatic isocyanates, which can also be substituted with other organic or inorganic groups that do not adversely affect the course of the urethane forming reaction. The isocyanate material has a functionality of between 2 and 3 and is used in an amount to provide a NCO/OH equivalents ratio of between about 0.95:1 and about 1.5:1 and preferably between'about 1.0:1 and about 1.2:1.

A prepolymer can be employed as the isocyanate. An isocyanate terminated prepolymer can be formed by adding an excess of diisocyanate (e.g. tolylene diisocyanate) to the hydroxyl-terminated diene homopolymer or copolymer.

Inorganic fillers are added in order to control viscosity and prevent overpenetration into the carpet fibers. Among the fillers which can incorporated into the adhesive compositions of this invention include calcium carbonate, talc, clay, silica, zinc oxide, feldspar, asbestos, carbon black and mixtures of these fillers. In addi tion, fillers such as titanium dioxide, hydrated alumina and barium sulfates can be employed. Generally, the amount of filler utilized is between about 40 and about 800 parts per parts by weight of the liquid, hydroxyl-terminated diene polymer and preferably the amount of filler is between about 100 and about 600 parts per hundred parts by weight of hydroxylterminated diene polymer. The fact that high filler levels can be employed means that a significant economic advantage can be obtained using large amounts of inexpensive filler in the formulation.

In order to keep the viscosity from becoming too high with the filler loads utilized in connection with the invention up to about 200 and preferably up to about 100 parts of a hydrocarbon oil per 100 parts by weight of diene polymer are added. Preferably such hydrocarbon oil is a naphthenic or aromatic oil which has a viscosity at 100 F. of between about 50 and about 2,500 Saybolt universal seconds and preferably between about and about 1,500 Saybolt seconds. Because of odor characteristics, naphthenic oils are the preferred mate rials. Paraffinic oils can be used, but occasionally a compatibilty problem occurs with such oils. Since oil extension, which is desirable for lowering costs and improving processibility, sometimes tends to be harmful to certain physical properties, including adhesion and tuft lock, higher molecular weight extenders can be used to replace part or all of the oil employed. Examples of such extenders include asphalt, vulcanized vege table oils, facticeand lower molecular weight polystyrene.

Catalysts employed in connection with compositions of the present invention in order to provide the necessary acceleration of cure time include triethylene diamine (DABCO), various tin, lead and zinc containing catalysts such as dibutyl tin dilaurate, nickel acetyl acetonate, ferric acetyl acetonate, stannous octoate, cobalt naphthenate and the like as well as combinations of such catalysts. The amount of catalyst employed depends on the desired rate of cure at the curing temperature. Generally, catalyst is used in an amount varying between about 0.02 and about 4 parts per 100 parts by weight of the liquid, hydroxyl-terminated diene polymer and preferably is employed in an amount between about 0.1 and about 2.0 parts per 100 parts by weight of the diene polymer.

Water can also be added to the compositions to create a polyurethane foam or sponge. Specifically, between and about 10 parts of water per 100 parts by weight of the liquid, hydroxyl terminated diene polymer can be incorporated in the composition. Preferably, water is incorporated between about 1.0 and about 8 parts per hundred parts by weight of the diene polymer. Since the isocyanate moiety is sensitive to water, the isocyanate should be essentially isolated from water, air and the like before reaction. In addition, the diene polymer and other reactants, and particularly the fillers, which can contain variable amounts of water, should be dried or degassed in a vacuum to remove moisture before the reaction. The preferred procedure is to remove all the moisture from the ingredients and then incorporate the desired amount of water into the reaction mixture. By following this procedure it is possible to know precisely how much water is in the composition, and it is accordingly possible to obtain consistent results for each formulation.

Generally when larger amounts of high molecular weight polyol are used, amounts of the other ingredients used are at the upper end of the ranges listed above. Conversely, when low amounts of high molecular weight polyol are used, amounts of the other ingredients are at the lower end of the ranges listed above. These various amounts are adjusted to provide workable viscosities, desirable cure times, and required fire retardancy, etc. for each specific application.

Economically, it is often desirable to also incorporate various inhibitors and other conventional additives in the adhesive composition of the present invention. For example, oxidation inhibitors can be added to improve aging characteristics. Such inhibitors include alkylated phenol and aromatic amines.

Other substances, which can be added to the reaction mixture are pigments, plasticizers, surfactants, stabilizers and the like. Surfactants, for instance, can be added in order to increase the penetration of the adhesive composition in the backing cloth or primary fabric and around the pile so as to firmly bind the pile to the backing cloth. Surfactants, such as various silicone materials, serve to stabilize bubble formation. In some instances small amounts of diluting agents, which decrease the viscosity of the reaction mixture, can also be added to increase penetration. Emulsifiers can be incorporated to disperse limited soluble components. Dispersing aids can be incorporated to prevent filler settlement. in addition, dehydrating agents such as molecular sieves or zeolite materials, e.g., Linde 5A molecular sieve, can be incorporated in order to regulate water content. Preferably these materials are incorporated in the polyol blend, as hereinafter defined.

Generally, all ingredients except the isocyanate are preblended. This is commonly called the polyol blend. Conventional procedures can be employed for mixing or blending the ingredients for the polyol blend, including the use of double planetary arm mixers and Cowles high speed mixers. The order of mixing can be varied to suit the characteristics of the mixing equipment being used. The powder material can be blended with a little liquid to obtain a good dispersion and then the remainder of the liquid is added or liquid can be blended and then the powder material is incorporated. Mixing times will vary depending on the efficiency of the mixing equipment and the type of filler used. The power material can be blended with a little liquid to obtain a good dispersion and then the remainder of the liquid is added or liquid can be blended and then the powder material is incorporated. Mixing times will vary depending on the efficiency of the mixing equipment and the type of filler used.

As previously indicated the isocyanate moiety is sensitive to water and accordingly in the preferred practice moisture is initially removed from the reactants. Alternatively, the reactants can be mixed and then degassed, usually in a vacuum, to remove air bubbles and moisture from the mixture. Following this procedure a mixture can be degassed in a steam jacket kettle maintained under a vacuum of 10 to 50 millimeters of mercury for a time period which can be up to about 2 hours. Sometimes thin film evaporator type equipment is used to remove moisture.

The viscosity of the resulting adhesive composition after the isocyanate is added to the polyol blend is between about 3,000 and about 100,000 centipoises and preferably between about 8,000 and about 50,000 centipoises as measured using a Brookfield viscosity device, Model RVT, operated at S'rpm (revolutions per minute) using a number 5 spindle. The viscosity measurement is made before catalyst is added to the composition so as to eliminate the effects of polymerization. The Brookfield viscometer and its operation are described in Development of Research Technique for Evaluating the Low Temperature F luidity of Automatic Transmission Fluids published by Coordinating Research Council, Inc., February 1963, Appendix A. The thixotropic ratio for the adhesive composition should be high enough that filler does not settle out of the composition and also high enough to prevent overpenetration of the carpet while being low enough to enable the adhesive composition to be pumped, readily blended, and easily applied by doctoring procedures conventional in the art. The thixotropic ratio determined by viscosity measurements made at 1 and at 20 revolutions per minute is between about 1.3:1 and about 10:1 and preferably between about 2:1 and about 8:1. Among the thixotropic agents which can be incorporated to achieve the desired viscosity and the aforementioned ratio are clays, such as kaolin; asbestos; amines; and silica.

To apply the reactive ingredients to the carpet, the polyol blend and the isocyanate are preferably accurately metered and mixed in a multi-component mixmeter machine and continuously and immediately fed by hose onto the underside of carpet (underside being up). If desired, the catalyst, or water, or other components (including fire retardant compound) can be fed into a multi-component mix meter machine as separate accurately metered streams. To assure better mixing a portion of the extender oil can be incorporated with the isocyanate. Usually the ingredients are applied at a temperature between room temperature and about 150 F. Preferably the temperature of application is between about and about F.

After the adhesive composition has been applied to the underside of pile fiber or primary fabric substrate the adhesive composition is then conventionally spread with a doctor blade. As the mixture passes under the blade, the shearing action of the blade reduces the viscosity so that the mixture can be forced down into and around the tufts of yarn. After passing under the blade, the original high viscosity is regained preventing undesirable overpenetration. The amount of adhesive composition applied is normally just sufficient to obtain adequate adhesion of the pile fibers to the primary fabric substrate. Excess adhesive composition is not only wasteful, but also can cause penetration of the primary fabric, rendering yarn stiff and the final carpet unacceptable. Typically, coating weights for carpets vary from about 12 to about 37 ounces per square yard. Preferably, however, the amount of adhesive composition applied to the carpet ranges from about 20 to about 30 ounces per square yard. In effect the lower limit with respect to the amount applied is limited by the amount necessary to adequately achieve the desired goal, whether it be that of a laminating adhesive, precoat composition or unitary backing.

Curing time and temperature can be varied. Normally, curing is accomplished at a temperature in the range between about 225 and about 350 F. and preferably in the range of from about 275 to about 325 F. for a period of about 0.3 to about 3 minutes. An oven or heated drum can be used for curing.

Among the properties of a carpet which are directly affected by the nature of the adhesive applied are tuft lock, anti-fray properties, appearance and dimensional stability. Whereas closely woven carpets of high pile density may have adequate tuft lock retention without application of an adhesive, tufted carpets have virtually no tuft retention in the absence of an adhesive. Antifray properties are important with respect to the elimination of fraying of cut edges of tufted carpets. To achieve complete anti-fray characteristics, appreciable weight of adhesive coating is normally required. The appearance of a carpet is judged by hand and visual appearance after being laid. Certain adhesive compositions can provide a better hand to a carpet by introducing a certain degree of stiffness in the carpet. In addition, carpet stiffness also tends to prevent buckling, imparts a high degree of resilience and prevents slipping on a polished floor. Dimensional stability of a carpet is obtained by locking the fibers together.

In addition to other requirements, the adhesive employed for carpets must have long effectiveness and should have a high tensile strength. In addition, the adhesive should not be degraded by water or other common solvents which could be spilled on carpeting or with which the carpet is likely to come in Contact. Moreover, the adhesive composition must be capable of application by simple conventional techniques. Thus, in addition to good adhesion characteristics, adhesive compositions must be judged by other criteria.

Some of the important characteristics of adhesive compositions utilized for carpet backing applications are T-peel, tuft lock and pill test. T-peel is a value obtained when the secondary fabric backing is pulled away from the primary fabric backing. This value is determined using a Scott tester. Adhesion of the scrim or secondary fabric backing to the primary fabric is referred to as the peel strength. This expression is used in its normal sense in the carpet manufacturing industry to mean the force required to peel apart a strip of two adhered components two inches wide which have been aged 24 hours. It is measured by gripping components in separate jaws of the Scott tensile tester and then moving the jaws apart at a rate of two inches per minute. A value of between 6 and pounds is normally obtained. Generally, the lighter the coating weight, the lower the T-peel. Tuft lock is a determination of the ability of the rug backing adhesive composition to hold fiber to both the primary and secondary fabric backing material. Tuft lock is determined by using a Scott tester to pull on one tuft of the pile to measure the force required to pull the tuft away from the primary and secondary fabric backing material. Normally, values for styrene-butadiene rubber latex will vary from 6 to 15 pounds of pull. At 20 to 30 pounds of pull, the yarns used in the carpet industry usually break.

The pilling test is a determination of the ability of rug backing composition to completely enclose individual fibers. Should the fibers in the construction not be completely enclosed, mild rubbing of the carpet produces loose strands of fibers which tend to form into a small ball of fiber or a pill.

The invention will be illustrated by the following examples, it being understood that there is no intention to be necessarily limited by any details thereof, since variations can be made within the scope of the invention.

EXAMPLE I A thixotropic adhesive composition was prepared by blending parts by weight of a liquid, hydroxylterminated polybutadiene (Resin R-45HT, manufactured by ARCO Chemical Company) having an equivalent weight of 1180, a hydroxyl content of 0.85 milliequivalents per gram, and 0.05 weight percent moisture; with 24 parts by weight of bisisopropanol isophthalate having an equivalent weight of 141 grams; 196 parts by weight of naphthenic process oil (Acme S-60 oil, manufactured by Atlantic Richfield); 310 parts by weight of calcined kaolin (Glomax H. E., manufactured by Georgia Kaolin Company); 0.02 parts by weight of dibutylin dilaurate (T-12, manufactured by MeT Chemical Company); and 43.8 parts by weight of diphenyl methane 4,4'-diisocyanate (isonate 143-L, manufactured by Upjohn Company), having an equivalent weight of 144 grams. This formulation can be used as an adhesive composition for rug and carpet backing applications.

EXAMPLE II A thixotropic adhesive composition was prepared by blending 100 parts by weight of R-45-HT resin (identitied in Example I) with 17.7 parts by weight of bisisopropanol aniline (lsonol C-100, manufactured by Upjohn Company) having an equivalent weight of grams; 118 parts by weight of saturated naphthenic process oil (Tufflo 6024 Oil, manufactured by Atlantic Richfield Company): 141 parts by weight of talc (Mistron Vapor, manufactured by United Sierra); 94 parts by weight of dry ground fatty acid treated calcium carbonate (Quincy-2-Electro, manufactured by Calcium Carbonate Company); 0.25 parts by weight of dibutyltin dilaurate; and 40.4 parts by weight of diphenyl methane 4,4 diisocyanate. The resulting adhesive formulation gave good adhesion of jute backing to carpet at a 15 ounce per square yard rate of application.

It was found that calcium carbonate (whiting) can be introduced at higher levels than clay (Example I) or talc without causing excessive viscosity increases and thus can be used to contribute to lower cost. The use of higher levels of calcium carbonate does not impart thixotropy and contributes little to reinforcement; hence a balance between the filler and calcium carbonate loadings must be achieved.

EXAMPLE III An adhesive formulation was prepared by blending 100 parts by weight of R-45HT resin (identified in Example I); 16.6 parts by weight of bisisopropanol aniline; 100 parts by weight of a low viscosity saturated naphthenic process oil (Tufflo 6004 Oil, manufactured by Atlantic Richfield); 100 parts by weight of dry ground calcium carbonate; 200 parts by weight of calcined kaolin; 1.06 parts by weight of water; 0.07 parts by weight of dibutyltin dilaurate; and 70.8 parts by weight of diphenyl methane, 4,4-diisocyanate.

The resulting adhesive composition had a NCO/OH ratio of 1.36. When applied at an application rate of 28 ounces per square yard, tuft lock equaled 12.7 pounds (average) and pounds (maximum). In addition, adhesion of the backing was excellent; jute was destroyed when attempting to delaminate double backed carpet.

Addition of water to the formulation of this example prior to isocyanate cure was found to be very beneficial for the following reasons:

a. The thixotropy of the uncured mix was greatly increased, presumably due to floculation of kaolin clay.

b. Tuft lock was increased. The same formulation without added water and the equivalent amount of diisocyanate had a maximum tuft lock of only 8.5 pounds. The water reaction contributes urea linkages to the polymer which should provide additional reinforcement.

c. Water reaction with isocyanate results in a chemical flow (foam formation) which appears to be beneficial since it increases the volume of the mix and allows lower application rates, provides continued blow after application which helps prevent voids between the carpet tufts. thereby resulting in more effective use of the adhesive, particularly if the foam is crushed at the proper stage of tackiness, and chemical blow brings the adhesive out of the tufts into contact with the secondary backing thereby assuring good adhesion of the latter to the carpet even if initial penetration of the mix is excessive.

EXAMPLE IV The following prepolymer precoat formulation was prepared and applied to red nylon carpet. The formulation consisted of 100 parts by weight of liquid, hydroxylterminated polybutadiene prepolymer having 8.3 weight percent free NCO groups (R-45HT resin identified in Example I reacted with tolylene diisocyanate); 13.5 parts by weight of bisisopropanol aniline; 2.9 grams of bisisopropanol bisphenol A; 100 grams of dry ground fatty acid treated calcium carbonate; and 2.5 parts by weight of 5A molecular sieve; 0.10 part by weight of dibutyltin dilaurate.

The resulting prepolymer composition had a NCO- lOH ratio of 1.1 and was cured for minutes at 220 F. It was applied to carpet at 28 ounces per square yard. The resulting tuft lock was 20 pounds while bundle wrap was 90 to 100.

EXAMPLE V A prepolymer precoat formulation was prepared in the following manner and applied to red nylon carpet. The formulation consisted of 100 parts by weight ofliquid. hydroxyl-terminated polybutadiene prepolymer (identified in Example IV); 13.5 parts by weight of bisisopropanol aniline; 11.6 grams of bisisopropanol bisphenol A; 100 grams of dry ground fatty acid treated calcium carbonate; 2.5 parts by weight ofSA molecular sieve; and 0.10 part by weight of dibutyltin dilaurate.

The resulting prepolymer formulation had a NCO- /OH ratio of 1.1 and was cured 30 minutes at a temperature of 220 F. It was applied to tufted nylon carpet at 28 ounces per square yard. The carpet had a tuft lock of 20 pounds and a bundle wrap of 75.

EXAMPLE VI A prepolymer adhesive precoat formulation was prepared in the following manner. 100 parts by weight of liquid, hydroxyl-terminated polybutadiene polymer (identified in Example IV) was mixed with 18 parts by weight of bisisopropanol aniline; 0.10 part by weight of dibutyltin dilaurate; 2 grams of silicone (GE SF 1156 surfactant); and 1 gram of water.

The resulting formulation had a NCO/OH ratio of 1.1. After being applied to blue nylon carpet the formulation was treated for 30 minutes at a temperature of 220;F. The coating was applied at 32 ounces per square yard. The resulting tuft lock was 15 pounds and a bundle wrap of 90 was obtained.

EXAMPLE VII A prepolymer adhesive precoat formulation was prepared by adding 100 parts by weight of liquid, hydroxyl-terminated polybutadiene prepolymer (identified in Example IV); 4.3 parts by weight of bisisopropanol aniline; 34.8 grams of bisisopropanol bisphenol A; 200 grams of dry ground fatty acid treated calcium carbonate; 2.5 grams of 5A molecular sieve; and 0.10 part by weight of dibutyltin dilaurate. i

The resulting prepolymer composition. having an- NCO/OH ratio of 1.1, was applied to blue nylon carpet and heated for 30 minutes at a temperature of 220 F.

. The coating was applied at 28 ounces per square yard.

A tuft lock measurement of 18 pounds and an average bundle wrap of 97 were obtained.

EXAMPLE VIII A prepolymer adhesive precoat formulation was prepared by adding 100 parts by weight of liquid, hydrox yl-terminated polybutadiene prepolymer (identified in Example IV); 4.3 parts by weight of bisisopropanol aniline; 34.8 grams of bisisopropanol bisphenol A; 100 grams of dry ground fatty acid treated calcium carbonate; 2 grams of silicone (GE SF 1156 surfactant); 1 gram of water; 2.5 grams of 5A molecular sieve; and 0.10 part by weight of dibutyltin dilaurate.

The resulting prepolymer composition, having an NCO/OH ratio of 1.1, was applied to blue nylon carpet and heated for 30 minutes at a temperature of 220 F. The coating was applied at 28 ounces per square yard. A tuft lock measurement of 14 pounds and an average bundle wrap of were obtained.

' The compositions of the foregoing examples had a viscosity between about 3,000 and about 100.000 centipoises as measured using a Brookfield Viscosity Device, Model RVT. operated at 5 rpm using a number 5 spindle. The thixotropic ratio of said compositions, determined by viscosity measurements made at 1 and at 20 rpm. was between about 1.3:1 and about 10:1.

From the foregoing it will be seen that this invention is well adapted to obtain all of the ends and objects hereinabove set forth, together with other advantages which are obvious or inherent in the system. Characteristics of formulations prepared in accordance with the present invention include a 12 to pound tuft lock; 75 to 100 percent bundle wrap; a backing destroying bond (i.e., the secondary fabric backing is torn upon attempted delamination); a good hand which is soft to firm without causing *boardiness"; a viscosity low enough to allow pumping, mixing and ease of application but high enough to prevent rapid uncontrolled penetration into the fibers (i.e., a thixotropic formulation); and rapid curing.

The thixotropic polyurethane adhesive compositions of the present invention have several advantages over the carboxylated styrene butadiene rubber latex adhesives which have been used for so many years. First the cure" of carboxylated latex adhesive is primarily a drying cycle which cannot be catalyzed in order to shorten the time. In contrast, the thixotropic adhesive compositions of the present invention cure through reaction with diisocyanate which can be catalyzed to any desired degree. Moreover, the cure, if sufficiently catalyzed, will take place rapidly at lower temperatures (e.g., 200 F.) Rapid cure increases production and greatly decreases capital investment since smaller curing ovens are required. Fuel requirements are also greatly reduced. The thixotropic adhesive compositions of the present invention also have the advantage of having a higher early green strength which thereby reduces the chances of accidental delamination. Application of the thixotropic adhesive compositions of the present invention is also simpler than application of carboxylated latex adhesives. The composition of the invention can be discharged onto a carpet continuously by means of a hose or nozzle and the resulting adhesive adjusted using a conventional doctor blade to give the desired rate of application and degree of penetration. Another advantage is the fact that smaller and simpler equipment can be used with the thixotropic adhesive compositions of the present invention and this means a reduction in capital investment and required operators, thus reducing production costs.

Obviously, many modifications and variations of the invention as hereinbefore set forth can be made without departing from the spirit and scope thereof.

What is claimed is:

1. Carpet including a primary backing material, tufted yarn stitched through the primary fabric backing to provide a pile surface on one side of the primary backing and a loop of yarn on the underside of the primary backing and a layer of thixotropic adhesive composition adhered to the underside of the primary backing and the loop of yarn, said thixotropic composition having a thixotropic ratio based on the viscosity at 1 rpm and at 20 rpm of between 1.3:1 and 10:1, said composition comprising liquid, hydroxyl-terminated diene polymer; high molecular weight polyol having an average equivalent weight between about 500 and 2,200 present in an amount of about 0.1 to 5 times the equivalents of the diene polymer; low molecular weight polyol having an equivalent weight of between about 50 and about 300 present in an amount between about 1.5 and about 8 times the equivalents of diene polymer; isocyanate having a functionality of between 2 and 3 present in an amount to provide a NCO/OH equivalents ratio of between 0.95:1 and 1.5:1; filler present in an amount between about and about 600 parts per 100 parts by weight of diene polymer; oil extending hydrocarbon liquid present in an amount of up to 200 parts per 100 parts by weight of diene polymer; water present in an amount of about 1.0 to 8 parts per 100 parts by weight of diene polymer; and catalyst for said composition present in an amount between about 0.02 and about 4 parts per 100 parts by weight of the diene 

1. CARPET INCLUDING A PRIMARY BACKING MATERIAL, TUFTED YARN STITCHED THROUGH THE PRIMARY FABRIC BACKING TO PROVIDE A PILE SURFACE ON ONE SIDE OF THE PRIMARY BACKING AND A LOOP OF YARN ON THE UNDERSIDE OF THE PRIMARY BACKING AND A LAYER OF THIXOTROPIC ADHENSIVE COMPOSITION ADHERED TO THE UNDERSIDE OF THE PRIMARY BACKING AND THE LOOP OF YARN, SAID THIXOTROPIC COMPOSITION HAVING A THIXOTROPIC RADIO BASED ON THE VISCOSITY AT 1 RPM AND AT 20 RPM OF BETWEEN 1.3:1 AND 10:1, SAID COMPOSITION COMPRISING LIQUID, HYDROXYL-TERMINATED DIENE POLYMER, HIGH MOLECULAR WEIGHT POLYOL HAVING AN AVERAGE EQUIVALENT WEIGHT BETWEEN ABOUT 500 AND 2,200 PRESENT IN AN AMOUNT OF ABOUT 0.1 TO 5 TIMES THE EQUIVALENTS OF THE DIENE POLYMER, LOW MOLECULAR WEIGHT POLYOL HAVING AN EQUIVALENT WEIGHT OF BETWEEN ABOUT 50 AND ABOUT 300 PRESENT IN AN AMOUNT BETWEEN ABOUT 15 AND ABOUT 8 TIME THE EQUIVALTS OF DIENE POLYMER, ISOCYANATE HAVING A FUNCTIONALITY OF BETWEEN 2 AND 3 PRESENT IN AN AMOUNT TO PROVIDE A NCO/OH EQUIVALENTS RATIO OF BETWEEN 0.95:1 AND 1.5:1 FILLER PRESENT IN AN AMOUNT BETWEEN ABOUT 100AND ABOUT 600 PARTS PER 100 PARTS BY WEIGHT OF DIENE POLYMER, OIL EXTENDING HYDROCARBON LIQUID PRESENT IN AN AMOUNT OF UP TO 200 PARTS PER 100 PARTS WEIGHT OF DIENE POLYMER, WATER PRESENT IN AN AMOUNT OF ABOUT 1.0 TO 8 PARTS PER 100 PARTS BY WEIGHT OF DIENE POLYMER, AND CATALYST FOR SAID COMPOSITION PRESENT IN AN AMOUNT BETWEEN ABOUT 0.02 AND ABOUT 4 PARTS PER 100 PARTS BY WEIGHT OF THE DIENE POLYMER. 